The present invention relates to a digital signal recording/reproducing apparatus for recording digital signals on a recording medium and/or reproducing the signals from the medium, or in particular to a digital signal recording apparatus having the function of protecting the copyright of the digital signal recorded in a recording medium.
The recent progress of the research on the compression of video and audio data using the digital technique has facilitated the storage and transmission of the data. This has greatly promoted the digitization of the broadcasting techniques.
A system is known, for example, in which analog video and audio signals are encoded by digital compression with high efficiency using the MPEG (moving picture experts group) standard and broadcast through a satellite or a coaxial cable. An apparatus for receiving the digital broadcasting is a digital broadcast receiver called the set top box.
A technique for receiving the digital signal transmitted with a plurality of information multiplexed to select the desired program is described in JP-A-8-56350.
As a home-use apparatus for recording and reproducing video and audio signals, on the other hand, an optical disc recorder is under development, which is capable of recording and reproducing the digital video and audio signal compressed and encoded digitally for the digital TV broadcasting, etc.
The digital broadcast receiver and the optical disc recorder are connected to each other by a digital interface, and are capable of storing the received digital broadcast with a high quality. The digital signal transmitted through a digital interface, if fee-charging or the need arises otherwise, requires protection to prevent illegal duplication.
A method for protecting the digital signal transmitted through the digital interface is described, for example, in “5C Digital Transmission Content Protection White Paper, Revision 1.0, Jul. 14, 1998”.